Method for producing a ceramic crucible

a technology of ceramic crucibles and crucibles, which is applied in the field of ceramic crucible production methods, can solve the problems of only being used, unable to meet the requirements of use, and known methods are relatively cost-intensive, and achieve the effects of low cost, small dimensional tolerance, and easy and cheap production

Inactive Publication Date: 2006-06-29
BEGO BREMER GOLDSCHLAGEREI WILH HERBST
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0025] An advantage of the invention (in its various aspects) is that the casting moulds to be used are easy and cheap to produce and may be used to produce a virtually unlimited number of ceramic crucibles. This makes cost-effective manufacture possible. In addition, small dimensional tolerances may be achieved, i.e., as explained above, two ceramic crucibles produced using a method according to the invention differ only slightly in their dimensions. In addition, it is advantageous that a high degree of shape accuracy and thus small shape tolerances may be achieved. This means that two ceramic crucibles produced using a method according to the invention differ only slightly in shape. A further advantage is that smooth surfaces may be achieved.
[0026]FIG. 1 shows a casting mould for use in a method according to a practical example of the invention.

Problems solved by technology

A disadvantage of this method is that the plaster mould used is complex to produce and can only be used to produce a limited number of ceramic crucibles.
This makes known methods relatively cost-intensive.
In addition, as the plaster mould ages changes occur to the crucible geometry and surface, such that the ceramic crucibles produced exhibit only poor dimensional accuracy.
Poor dimensional accuracy means that ceramic crucibles produced by the same method may differ greatly in their geometric dimensions from one another and from the average geometric dimensions of the ceramic crucibles produced.
Poor dimensional accuracy is therefore synonymous with such a method exhibiting poor reproducibility with regard to the ceramic crucibles produced.
If a method exhibits poor reproducibility, it is impossible to achieve small dimensional tolerances.
Furthermore, the methods according to the prior art do not allow the achievement of small shape tolerances.
Ceramic crucibles produced using methods according to the prior art additionally exhibit an uneven surface, which is disadvantageous with regard to subsequent use.
A further disadvantage is that the wall thickness may vary from place to place, which contributes to poor shape accuracy.

Method used

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  • Method for producing a ceramic crucible
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Examples

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example 1

Practical Example 1

[0084] A method is described below for producing a ceramic crucible according to a practical example of the present invention. An aqueous silicon dioxide sol is mixed with aluminum oxide powder and mullite powder by stirring; glycerol is added.

[0085] The median value (d50) of the distribution of the diameters of the SiO2 particles in the aqueous SiO2 amounts to 8 nm. The diameters of the aluminum oxide powder particles are less than 10 μm and the diameters of the mullite powder particles are less than 80 μm. Such a sol is produced industrially, for example by acidifying aqueous sodium silicate solutions, passing the solution over cation exchangers and alkalizing the resultant sol. Such a sol is sold by CWK as Kostrosol 08 / 30.

[0086] The mixture has the composition stated in Table 1:

TABLE 1Materialgwt. %Mullite10050.9Aluminium oxide4522.9SiO2 sol5025.4Glycerol1.50.8Total196.5100.0

[0087] The mixture is a freeze-castable slip, i.e. a special solidifiable slip. The...

example 2

Practical Example 2

[0093] A further practical example of a method according to the invention is described below. First of all, an aqueous SiO2 sol is mixed with aluminum oxide, mullite and Nb powder by stirring; glycerol is added. The diameters of the aluminum oxide, mullite and SiO2 particles are those stated in practical example 1. The diameter of the niobium particles is less than 40 μm.

TABLE 2Materialgwt. %Mullite10050.4Aluminium oxide4522.7SiO2 sol5025.2Glycerol1.50.7Nb21.0Total198.5100.0

[0094] The slip produced in this way is poured into a metallic casting mould as in practical example 1 and frozen at −40° C. in the freezing compartment. The resultant preform is demoulded and then dried in a drying cabinet at 60° C., 1013 hPa and 30% relative atmospheric humidity. The preform is then air-sintered for 3 hours at 1200° C. During sintering the Nb powder oxidises (due to the presence of atmospheric oxygen) with an increase in volume to yield niobium pentoxide.

example 3

Practical Example 3

[0095] A further practical example of a method according to the invention is described below. First of all an aqueous SiO2 sol is mixed with aluminium oxide, mullite, Nb and AlMg5 powder by stirring. The diameter of the AlMg5 powder particles is less than 80 μm. The diameters of the other particles correspond to those stated in practical example 2.

TABLE 3Materialgwt. %Mullite10045.8Aluminium oxide4520.6SiO2 sol5022.9Glycerol1.50.7Nb20.9AlMg5209.1Total218.5100.0

[0096] The slip produced in this way is poured into a metallic casting mould as in practical example 1 and frozen at −40° C. by cryostat. The resultant preform is demoulded and then dried in a drying cabinet at 60° C., 1013 hPa and 30% relative atmospheric humidity. The preform is then firstly heated for 2h to 600° C. to 700° C. and then air-sintered for 3 hours at 1200° C. While the preform has a temperature of 600° C. to 800° C., the AlMg5 powder liquefies and oxidises with an increase in volume to yield...

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Abstract

The invention relates to a method for producing a ceramic crucible. The following steps are proposed: providing a solidifiable slip, providing a casting mould (10) for the ceramic crucible, pouring the slip into the casting mould, solidifying the slip in the casting mould by (a) freezing and / or (b) changing its pH value, such that a preform is obtained, and heat-treating the preform, such that a ceramic crucible is obtained. The invention additionally relates to a ceramic crucible producible using such a method and a kit for producing such a ceramic crucible, having: (a) a casting mould, preferably a metal mould, for a ceramic crucible, (b) a sol, preferably an aqueous SiO2 sol, comprising a ceramic nanoparticle fraction, (c) ceramic particles comprising a microceramic fraction, (d) optionally a metal powder consisting essentially of metals and / or alloys and / or intermetallic compounds, (e) optionally one or more further additives and optionally organic or inorganic binders. Finally, the invention relates to an apparatus for performing the stated method.

Description

FIELD OF THE INVENTION [0001] The invention relates to a method for producing a ceramic crucible. Furthermore, the invention relates to a ceramic crucible, a kit for producing a ceramic crucible and an apparatus for performing a method for producing a ceramic crucible. BACKGROUND OF THE TECHNOLOGY [0002] It is known to produce ceramic crucibles by pouring a slip into a porous, absorbent plaster mould. The slip comprises suspending fluid, which is absorbed by the absorbent plaster mould. Through extraction of the suspending fluid, a ceramic layer forms on the wall of the plaster mould, which continues to build up until the desired layer thickness of the ceramic layer is reached, whereupon the resultant green body is de-moulded and then sintered, producing a ceramic crucible. [0003] According to one variant, a hollow casting plaster mould is used as the plaster mould. Once the slip has been poured in and the desired wall thickness has-been reached for the resultant green body, the sup...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): B01L3/00C21B3/00C04B35/64
CPCB28B1/007B28B7/40B82Y30/00C04B35/185C04B35/624C04B35/62655C04B2235/3206C04B2235/3217C04B2235/3222C04B2235/3251C04B2235/3418C04B2235/3463C04B2235/401C04B2235/402C04B2235/404C04B2235/5436C04B2235/5454C04B2235/80
Inventor SCHLUTER, MARTINWIEST, THOMASDIERKES, STEPHAN
Owner BEGO BREMER GOLDSCHLAGEREI WILH HERBST
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